Tractor and printer equipped with the same

ABSTRACT

According to one embodiment, a tractor comprises a pin belt, a pair of rotating units and a roller. The pin belt configured as an endless belt, which has a plurality of pins on the outer peripheral surface thereof, wherein the pins are respectively inserted into feeding holes formed on a tractor paper, and the pin belt rotates to convey the tractor paper. The pair of rotating units configured to rotate the pin belt. The roller, which is arranged between the pair of rotating units, with a groove on the outer peripheral surface thereof, wherein the front end of the pin is fitted into the groove, so that the front end of the pin is abutted against the groove to space between the outer peripheral surface of the pin belt and the outer peripheral surface of the roller.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims the benefit ofpriorities from the prior Japanese Patent Applications No. 2011-116026filed on May 24, 2011 and No. 2012-037865 filed on Feb. 23, 2012, theentire contents of which are hereby incorporated by reference.

FIELD

Embodiments described herein relate to a tractor and a printer which isequipped with the tractor.

BACKGROUND

Conventionally, a printer equipped with a tractor, which conveys atractor paper, using a pair of left and right rotating pin belts is wellknown. Feeding holes are respectively formed at the opposite sides ofthe width direction of the tractor paper along a paper feeding direction(conveying direction). Moreover, a plurality of pins is formed on theouter peripheral surfaces of the pin belt pair along the lengthdirection of the pin belt at regular intervals.

Furthermore, the pins on the outer peripheral surfaces of the pin beltpair are respectively inserted into the feeding holes of the tractorpaper and the pin belts are rotated so as to convey the tractor paper inthe conveying direction.

However, there is a printer which uses, for the sake of saving space, atractor that conveys a tractor paper by curving the tractor paper alonga guide surface curved into a concave arc shape. This tractor isprovided with a roller that presses pin belt to curve the rotation trackof the pin belt. Moreover, a groove for accommodating pins is configuredin the roller, the outer edge of which is abutted against the outerperipheral surface of the pin belt at the position where the pin belt isabutted against the roller to curve the pin belt (a bend) and the pinbelt is driven in the conveying direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a business machine provided with thetractor of an embodiment;

FIG. 2 is a perspective view of the tractor;

FIG. 3 is a side-sectional view of a belt unit;

FIG. 4-1 is a sectional view of the conventional roller and pin belt ona straight line 30, this Figure showing the roller and the pin beltbetween which no tractor paper is inserted;

FIG. 4-2 is a sectional view of the conventional roller and pin belt onthe straight line 30, this Figure showing the roller and the pin beltbetween which a tractor paper is inserted;

FIG. 5 is a sectional view of the roller and the pin belt on thestraight line 30 according to the embodiment;

FIG. 6 is a diagram showing an example of the pin belt of which theheight of the pin is changed;

FIG. 7 is a sectional view of an example of a roller in another shape;

FIG. 8 is a cross-sectional view of a belt unit in case that theconveying path of a tractor paper is not curved.

DETAILED DESCRIPTION

According to one embodiment, a tractor comprises a pin belt, a pair ofrotating units and a roller. The pin belt configured as an endless belt,which has a plurality of pins on the outer peripheral surface thereof,wherein the pins are respectively inserted into feeding holes formed ona tractor paper, and the pin belt rotates to convey the tractor paper.The pair of rotating units configured to rotate the pin belt. Theroller, which is arranged between the pair of rotating units, with agroove on the outer peripheral surface thereof, wherein the front end ofthe pin is fitted into the groove, so that the front end of the pin isabutted against the groove to space between the outer peripheral surfaceof the pin belt and the outer peripheral surface of the roller.

FIG. 1 is a perspective view of a business machine 1 provided with thetractor 9 according to the embodiment. As shown in FIG. 1, the businessmachine 1 according to this embodiment comprises a main body unit 3, akeyboard 4 and a display 5.

The main body unit 3 and a printer unit (not shown) of a computer areaccommodated in the frame 2 of the main body unit 3. A paper feedingport 7 for feeding a lengthwise tractor paper 6 (refer to FIG. 2) isformed at a position of the frame 2 opposite to the display 5. A tractor9 for conveying the tractor paper 6 is accommodated in the frame 2. Apaper outlet 8 is formed on the upper part of the frame 2 to feed outthe tractor paper after it is fed into the frame 2 from the paperfeeding port 7 and is printed. Further, another paper feeding port (notshown) is also configured below the display 5 in this embodiment. Theother conveying unit (not shown) different from the tractor 9 uses theroller to convey the paper inserted by an operator from the paperfeeding port below the display 5 and discharges the printed paper fromthe paper outlet 8.

FIG. 2 is a perspective view of the tractor 9. The tractor paper 6printed by the printer unit of the business machine 1 is a strip-shapedpaper on which a perforation (not shown) is formed along the widthdirection of the paper to be able to cut the paper apart and a pluralityof the perforations are formed in the length direction of thestrip-shaped paper at regular intervals.

A slip paper that a plurality of papers are laminated can be taken as anexample of the tractor paper 6. A plurality of regularly spaced feedingholes 6 b are formed at opposite sides of the tractor paper 6 along thelength direction of the tractor paper 6. The tractor paper 6 is foldedin a zigzag state and is placed at the side of the business machine 1.

The tractor 9 pulls out the tractor paper 6 from the top of the foldedtractor paper and then successively conveys the tractor paper 6.

As shown in FIG. 2, the tractor 9 mainly comprises a pair of belt units11 provided with pin belt (refer to FIG. 3), a guide unit 12 and atransmission shaft 13.

The transmission shaft 13 is configured across the pair of belt units11. Moreover, the guide unit 12 is supported at the center of thetransmission shaft 13 in the axial direction by a fixing device (notshown). Another transmission shaft (not shown) may also be configuredacross the pair of belt units 11.

The belt unit pair 11 is kept in parallel with one the other through thetransmission shaft 13. The operator can change the space between thebelt unit pair 11 by sliding either of the belt unit pair 11 along thetransmission shaft 13. Thus, the operator can align the belt unit pair11 with the opposite sides 6 a of the tractor paper 6 according to thewidth of the tractor paper 6 so as to set the feeding holes 6 b of thetractor paper 6 on the pin belt 14 (refer to FIG. 3) of the left andright belt units 11.

The guide unit 12 is arranged in the middle of the left and right beltunits 11. The guide unit 12 supports, from the below, the substantiallycentral part of the tractor paper 6 retained by the belt unit pair 11.

Thereby, it is able to prevent the application of a tension to theopposite sides 6 a of the tractor paper 6 by the tractor paper 6 whichis bent under its own weight.

The belt unit pair 11 and the guide unit 12 are both curved into a bowshape, and the tractor paper 6 is conveyed from the paper feeding port 7to the paper outlet 8 (refer to FIG. 1) along the curved shape.

As shown in FIG. 2, each of the belt unit pair 11 comprises a base 15, afixed cover 16, a movable cover 17 and a roller retainer 19. A shaft 13runs through the roller retainer 19.

The movable cover 17 is rotationally supported on the base 15 of each ofthe belt unit pair 11 via a hinge unit 15 b. Under the force applied bythe operator manually, the movable cover 17 reciprocates between thevertical opening position represented by the dotted line shown in FIG. 2and the horizontal closing position represented by the solid line shownin FIG. 2. The hinge unit 15 b is configured on each of the belt unitpair 11 at a position outside the width direction of the tractor paper6. Moreover, the rotation shaft of the hinge unit 15 b is configuredalong the two ends of the tractor paper 6 in the width direction, thatis, the opposite sides 6 a of the tractor paper 6.

Therefore, the two movable covers 17 arranged on the belt unit pair 11are opened like a butterfly formation door (double door) from thehorizontal closing position toward the outside and upside of the widthdirection of the tractor paper 6 like the two movable covers 17 faceeach other in the width direction of the tractor paper.

The movable cover 17 is manually opened by the operator, as describedabove, to respectively fit the feeding holes 6 b of the tractor paper 6onto the pins 14 b (refer to FIG. 3) of the pin belt 14 s, therebysetting the tractor paper 6 on the pin belt 14.

FIG. 3 is a side-sectional view of the belt unit 11, a part of which iscut away and is not shown in FIG. 3.

The base 15 supports the fixed cover 16, the movable cover and theroller retainer 19. Moreover, the base 15 rotationally supports therollers 20 and 20A (20) of a pair of rotating units that rotates the pinbelt 14. An endless pin belt 14 is rotationally extended between theroller 20 and the roller 20A. The roller 20A rotates anticlockwise underthe drive of a motor (not shown). When the roller 20A rotatesanticlockwise under the drive of the motor, the pin belt 14 rotates inthe direction indicated by an arrow shown in FIG. 3. The track that thepin belt 14 rotates in the direction indicated by the arrow shown inFIG. 3 is referred to as a rotation track of the pin belt 14. If therotating unit is composed of at least one pair, more than two rotatingunits may be used, and the rotating unit is not limited to the roller20, but may be formed in other shape.

The fixed cover 16 and the movable cover 17 are arranged to cover theupper portion of the base 15. The lower surface 16 a of the fixed cover16 and the lower surface 17 a of the movable cover 17 are oppositelyarranged at the positions that are a substantially fixed distance abovethe upper surface 15 a of the base 15. A conveying path 10 for conveyingthe tractor paper 6 is created between the lower surfaces 16 a and 17 aand the upper surface of the base 15, and thus the tractor paper 6 isconveyed in the conveying path 10 as the pin belts 14 rotate.

The tractor 9 acquires the tractor paper 6 fed from the paper feedingport 7 (refer to FIG. 1) and conveys the tractor paper 6 in theconveying path 10. Moreover, the tractor 9 conveys the tractor paper 6that is printed by a printer unit (not shown) in the conveying path 10to the paper outlet 8 (refer to FIG. 1), and then discharges the printedtractor paper 6 from the paper outlet 8.

The pin belt 14 is made of elastomer or other flexible materials. Thepin belt 14 comprises a strip shaped belt unit 14 a having a fixed widthand a plurality of pins that protrude, at given intervals, along acircumferential direction at the center part in the width direction ofthe belt unit 14 a. In the middle of the conveying path 10 (that is, thepart of the conveying path from a position nearby the lower portion ofthe movable cover 17 to a position nearby the lower portion of the fixedcover 16), the front end of the pin 14 b protrudes more upwards than theupper portion 15 a of the base 15. Therefore, the feeding holes 6 b ofthe tractor paper 6 are caught by the pins 6 b in the middle of theconveying path 10 so that the tractor paper 6 is driven in the conveyingpath 10 along with the rotation of the pin belts 14.

The roller retainer 19 between the rollers 20 and 20A supports adual-torsion spring 21 (hereafter referred to as spring 21) having twocoils. The coils of the spring 21 are respectively wound on the shafts22 of the rollers 18. An elastic force is applied to the roller 18 bythe spring 21 in a direction indicated by an arrow 40 (arrow direction)shown in FIG. 3 so that the roller 18 is abutted against the pin belt 41and presses the pin belt 41 towards the arrow direction 40. In such amanner, the roller 18 curves the rotation track of the pin belt 14towards the arrow direction 40. Moreover, the pin belt 14 is extendedbetween the two rollers 18.

As shown in FIG. 3, a groove 18 b and an outer edge 18 a defining thegroove 18 b are configured on the periphery of the roller 18.

When the tractor paper 6 is fed to the roller 18 along with the rotationof the pin belt 14, the roller 18 and the pin belt 14 rotatesynchronously to convey the tractor paper 6 out along the curved shapeof the pin belt 14 in the conveying direction of the conveying path 10.Moreover, at the curved part of the pin belt 14, the pin belt 14 isconveyed while the pins 14 b of the pin belt 14 are firmly fitted withthe groove 18 b of the roller 18.

In FIG. 3, a straight line 30 indicates the position where the centralline 14 c (refer to FIG. 5) of the pin 14 b and the shaft 22 of theroller 18 are aligned.

The pin belt 14 and the tractor paper 6 on the pin belt 14 are mostcurved at the position of the straight line 30. Moreover, the pin 14 bis most deeply fitted into the groove 18 b on the straight line 30.

The problems existing in the conventional roller 18 (918) are describedhere in supplement. FIG. 4-1 and FIG. 4-2 are sectional views of theconventional roller 918 and pin belt 14 on a straight line 30. As shownin FIG. 4, a groove 918 b and an outer edge 918 a defining the groove918 b are configured on the periphery of the roller 918. FIG. 4-1 showsa roller 918 and a pin belt 14 between which no tractor paper 6 isinserted, and FIG. 4-2 shows a roller 918 and a pin belt 14 betweenwhich a tractor paper 6 is inserted.

As shown in FIG. 4-1, in the conventional roller 918, the depth d3 ofthe groove 918 b is greater than the height (h) of the pin 14 b. Thus,the outer edge 918 a of the roller 918 is abutted against the belt unit14 a of the pin belt 14 to press the latter because the roller 918 isurged by the spring 21. Moreover, as shown in FIG. 4-2, if the tractorpaper 6 is inserted between the roller 918 and the pin belt 14, theroller 918 is pushed back with the elasticity of the spring 21 towardsthe direction reverse to the arrow direction 40 by a distance equal tothe thickness of the tractor paper 6. The outer edge 918 a of the roller918 is abutted against the tractor paper 6 to press the latter becausethe roller 918 is urged by the spring 21. In such a manner, the edges ofthe feeding holes 6 b of the tractor paper 6 are pressed by the outeredge 918 a of the roller 918 at the position nearby the curved part ofthe pin belt 14 where the roller 918 is located.

Especially, in the case where the tractor paper 6 is a slip paper suchas an invoice paper composed of a plurality of papers laminated or athick paper, the tractor paper 6 is hard to curve along the curved shapeof the pin belt 14. Therefore, at the curved part, the tractor paper 6is pressed into the roller 918 by the outer edge 918 a of the roller 918along the conveying direction and then conveyed. Therefore, a part oftractor paper 6 that is not completely curved is twisted and thus is aptto create wrinkle at the position nearby the blocked part of the paper 6by the outer edge 918 a of the roller 918.

In order to address this problem, it is considered to reduce the elasticconstant of the spring 21, however, the application of this solutionwill also lead to a problem that the pin 14 b may be apt to be slippedoff the feeding hole 6.

Next, the roller 18 of the present embodiment is described. FIG. 5 is asectional view of the roller 18 and the pin belt 14 of the embodiment onthe straight line 30. As described in FIG. 3, the outer edge 18 a andgroove 18 b are arranged on the periphery of the roller 18. That is, theouter periphery 18 e of the roller 18 consists of the surface of theouter edge 18 a and the bottom surface 18 c of the groove 18 b.Moreover, pins 14 b are formed in a protrusion manner on the outerperipheral surface 14 e of the belt unit 14 a of the pin belt 14.

As shown in FIG. 5, the groove 18 b of the roller 18 is abutted againstthe front end 14 d of the pin 14 b firmly fitted into the groove 18 b onthe straight line 30 (refer to FIG. 3). In such a manner, the roller 18presses the pin belt 14 in the arrow direction 40 to curve the rotationtrack of the pin belt 14. Under this state, the roller 18 of thisembodiment is located on the straight line 30 (refer to FIG. 3), and thesurfaces of the outer edge 18 a of the roller 18 and the belt unit 14 aof the pin belt 14 are arranged such that they are spaced by a distanced4.

With the depth d3 of the groove 18 b and the height h of the pin 14 b,the distance d4 is here expressed by the following formula: d4=h−d3.Thus, the distance d4 set between the outer edge 18 a of the roller 18and the belt unit 14 a must meet the following condition: d4=h−d3>0.Thus, the depth d3 of the groove 18 b of the roller 18 just needs tomeet the following condition: d3<h (Formula 1). That is, the distance d4can be set between the surfaces of the outer edge 18 a of the roller 18and the belt unit 14 a as long as the depth of the groove 18 b of theroller 18 is smaller than the height h of the pin 14 b.

Moreover, the distance d4 may also be greater than the thickness d5 ofthe tractor paper 6. In this case, the following formula must be met:d4=h−d3>d5. Thus, the depth d3 of the groove 18 b of the roller 18 justneeds to meet the following condition: d3<h−d5 (Formula 2).

As a more preferred embodiment, it is preferable that the distance d4 isset to be two times or three times the thickness (d5) of the tractorpaper 6. For example, in the case where the distance d4 is set to be ntimes the thickness d5, the following formula is met: d4=h−d3≧n*d5.Thus, the depth d3 of the groove 18 b of the roller 18 just needs tomeet the following condition: d3≦h−n*d5 (Formula 3). Moreover, n may bea natural number, a fraction or a decimal fraction.

In such a manner, the distance d4 can be set between the surfaces of theouter edge 18 a of the roller 18 and the belt unit 14 a as long as thedepth d3 of the groove 18 b of the roller 18 meets at least one of theforegoing formulae (1)-(3). Moreover, as a preferred embodiment, thedepth d3 of the groove 18 b should be determined at more than aprescribed depth (threshold level) so that the pin 14 b is not likely tobe slipped off the groove 18 b even the depth d3 of the groove 18 b isdecreased.

In the description above, the distance d4 is set based on the structureof the roller 18, but the distance d4 can also be set based on thestructure of the pin belt 14.

FIG. 6 is a diagram showing an example of a pin belt 214 having a pin214 b whose height (h) is changed. As shown in FIG. 6, at least one ofthe foregoing formulae (1)-(3) can be met by adjusting the height h ofthe pin 214 b. Moreover, the conventional roller 918 shown in FIG. 4-1can be used as long as at least one of the formulae (1)-(3) is met.

Thus, in the tractor 9 of this embodiment, the distance d4 is setbetween the outer peripheral surface 18 e of the roller 18 and the outerperipheral surface 14 e of the belt unit 14 a on the straight line 30where the pin belt 14 is most curved. Therefore, the tractor paper 6hardly twists even at a position where the tractor paper 6 is mostcurved and thus apt to twist.

The roller 18 may have other shapes that are not limited to the shapesshown in FIG. 5 and FIG. 6. FIG. 7 is a sectional view of an example ofthe roller 218 in another shape. As shown in FIG. 7, the groove 218 b ofthe roller 218 consists of a curved surface, the bottom of which isformed by the central portion abutted against the front end 14 d of thepin 14 b. Shaped like this, the front end 14 d of the pin 14 b isstabilized on the central line 218 c of the roller 218 to be preventedfrom moving transversely in the groove 218 b of the roller 218, thus,the roller 218 can rotate easily and smoothly.

Chamfers 218 d may be formed at the outer edge 218 a of the roller 218.That is, as shown in FIG. 7, the chamfers 218 d are formed on the outerperipheral surface of the roller 218 at the opposite sides along therotational center line 22 c of the roller 218. Moreover, the chambers218 d are formed into a circular shape along the outer peripheralsurface 218 e of the roller 218. Thus, the tractor paper 6 is hard totwist and thus does not generate a crease even after the tractor paper 6is floated off the pin belt 14. Moreover, R-shaped chamfers are adoptedas the chamfers 218 d in FIG. 7; however, the chamfers 218 d are notlimited to this shape, as another example, the chamfers 218 d may beC-shaped chamfers.

As stated above, in the tractor 9 of the above-described embodiment, thefront end of the pin 14 b is abutted against the groove 18 b formed onthe outer peripheral surface 18 e of the roller 18 so as to curve therotation track of the pin belt 14 and spaces the outer peripheralsurface 18 e of the roller 18 from the outer peripheral surface 14 e ofthe belt unit 14 a. The tractor paper 6 is not easily cause to twist orbe creased with wrinkles at the curved part of the pin belt 14 where theroller 18 is abutted against the pin belt 14, thus preventing theoccurrence of a crease.

Moreover, according to the tractor 9 of this embodiment, as the groove18 b of the roller 18 is abutted against the front end of the pin 14 bto curve the rotation track of the pin belt 14, the pin belt 14 can bedirectly pressed by the roller 18. Typically, the friction coefficientof the pin belt 14 is greater than that of the tractor paper 6, thus,compared with the approach of pressing the tractor paper 6 by the roller18, in the approach of directly pressing the roller 18 against the pin14 b of the pin belt 14 used herein, slipping is hard to be occurred onthe pin belt 14. Thus, compared with the conventional art in which thetractor paper 6 is conveyed by pressing the pin 14 b against the tractorpaper 6, in the present embodiment, the pin belt 14 can be easilypressed by the roller 18, and the tractor paper 6 can be easily fed out.

In addition, as the pin 14 b is abutted against the roller 18 in thiscase, the roller 18 may not be urged by the spring 21 in the arrowdirection 40. Thus, the components of the tractor 9 can be decreased bydirectly supporting the shaft 22 of the roller 18 by the roller retainer19.

Moreover, in the above embodiment, two rollers 18 are provided, but thenumber of the rollers may also be one (1) or more than two (2).

Although an exemplary miniaturized construction in which the tractor 9is accommodated in the frame 2 is described in the embodiment, the upperportion of the tractor 9 may protrude outside the frame 2. Moreover, theinstallation position, the shape and the installation posture of thetractor 9 are not limited to those described in this embodiment.Further, the business machine 1 may be a printer not having a computermain body unit.

Moreover, in the description above, the belt unit 11 and the guide unit12 are curved into a bow shape, and the conveying path 10 for conveyingthe tractor paper 6 is curved as well, however, this embodiment is alsoapplicable even the conveying path 10 is not curved as shown in FIG. 8.FIG. 8 is a cross-sectional view of the belt unit 11 having a non-curvedconveying path 10 for conveying the tractor paper. As shown in FIG. 8,the rotation track of the pin belt 14 may be linearly configured betweenthe rollers 20 and 20A. For instance, the roller 18 is used to press thetractor paper 6 on the upper surface 15 a of the base 15 to prevent thetractor paper from disjoining (floating off) from the conveying path 10during conveyance, however, the function of the roller 18 is not limitedto this.

Thus, even the conveying path 10 is not curved, like in the foregoingcase, the tractor paper 6 does not twist easily at the part where theroller 18 is abutted against the pin belt 14, the pin belt 14 can beeasily pressed by the roller 18 as well, and the tractor paper 6 can befed out easily.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments of the embodimentmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodiments ofthe embodiment may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A tractor, comprising: a pin belt configured as an endless belt,which has a plurality of pins on the outer peripheral surface thereof,wherein the pins are respectively inserted into feeding holes formed ona tractor paper, and the pin belt rotates to convey the tractor paper; apair of rotating units configured to rotate the pin belt; and a roller,which is arranged between the pair of rotating units, with a groove onthe outer peripheral surface thereof, wherein the front ends of the pinsare fitted into the groove, so that the front ends of the pins areabutted against the groove to space between the outer peripheral surfaceof the belt and the outer peripheral surface of the roller.
 2. Thetractor according to claim 1, wherein the depth of the groove of theroller is set to be smaller than the height of the pin so as to spacebetween the outer peripheral surface of the pin belt and the outerperipheral surface of the roller.
 3. The tractor according to claim 1,wherein the roller enables the front end of the pin fitted into thegroove to be abutted against the groove, thereby curving the rotationtrack of the pin belt.
 4. The tractor according to claim 1, wherein therotation track of the pin belt is linearly arranged between the pair ofrotating units.
 5. The tractor according to claims 2, wherein the depthof the groove of the roller is set to be d, the height of the pin is setto be h, the thickness of the tractor paper is set to be d1, and a givennumber is set to be n; the outer peripheral surface of the pin belt andthe outer peripheral surface of the roller are spaced by satisfying thefollowing condition: d≦h−n*d1.
 6. The tractor according to claims 1,further comprising: a chamfer part, which is formed on the oppositesides of the outer peripheral surface of the roller along the rotationalcenter line of the roller.
 7. The tractor according to claims 1, whereinthe cross-section of the groove is formed with curved concavity shaped.8. The tractor according to claim 2, wherein the roller enables thefront end of the pin fitted into the groove to be abutted against thegroove, thereby curving the rotation track of the pin belt.
 9. Thetractor according to claim 2, wherein the rotation track of the pin beltis linearly arranged between the pair of rotating units.
 10. The tractoraccording to claims 3, wherein the depth of the groove of the roller isset to be d, the height of the pin is set to be h, the thickness of thetractor paper is set to be d1, and a given number is set to be n; theouter peripheral surface of the pin belt and the outer peripheralsurface of the roller are spaced by satisfying the following condition:d≦h−n*d1.
 11. The tractor according to claims 4, wherein the depth ofthe groove of the roller is set to be d, the height of the pin is set tobe h, the thickness of the tractor paper is set to be d1, and a givennumber is set to be n; the outer peripheral surface of the pin belt andthe outer peripheral surface of the roller are spaced by satisfying thefollowing condition: d≦h−n*d1.
 12. A printer, comprising: a tractorclaimed in the claims 1; and a printer unit configured to print on thetractor paper conveyed by the tractor.